The present invention relates to a release mechanism for adjusting control of a drive shaft. More particularly, certain embodiments of the present invention relate to a release clutch that enables an operator to orbitally rotate a C-arm either manually or by a drive train.
Before and during a medical procedure, medical professionals may need to take several different images of a patient's body from a number of different orientations. Often it is difficult to effectively capture images from certain orientations where the imaging device is fixed and stationary. Therefore, imaging devices are mounted on large, mobile structures known as C-arm imaging machines. C-arm imaging machines typically include a mobile support structure, a carrier, and a curved, C-shaped positioning arm, or (C-arm). The carrier is mounted on the support structure and the C-arm is, in turn, slidably mounted to the carrier. An imaging source is located on one distal end of the C-arm and an imaging receiver is located on the other distal end of the C-arm. The C-arm imaging machine may be moved and rotated about a patient in a number of different orientations such that the patient is positioned between the imaging source and the imaging receiver. The C-arm imaging machine operator may then take an image of the patient.
The C-arm typically may be rotated about the patient in at least two ways. The support structure includes a rotation arm that is connected to the carrier. The C-arm has tracks along an outer periphery thereof that capture rollers on the carrier such that the C-arm is movably retained to the carrier along the rollers. A large belt extends from the carrier around the arms of the C-arm. The rotation arm may be rotated about a rotational  axis such that the C-arm also rotates about the rotational axis. This is known as the rotational rotation of the C-arm. Additionally, the C-arm may be rotated along the plane of the C-arm about a transverse axis by moving the belt such that the C-arm moves, or rotates, along the carrier. This is known as orbital rotation of the C-arm. By being rotatable about at least two different axes, the C-arm may be positioned at many different orientations about a patient in order to take images from different desirable perspectives. Thus, the mobile C-arm imaging machine greatly increases the efficiency and ease of taking images of a patient before and during a medical procedure.
However, the conventional mobile C-arm imaging machine has some drawbacks. First, conventional belt-driven C-arms may only be moved manually for orbital rotation. That is to say, an operator must manually release a brake and then manipulate the C-arm to move the C-arm to a desired position. The operator then manually stops the movement of the C-arm when it reaches its desired position and activates the brake to lock the C-arm in place. While this method of adjusting the position of the C-arm may be desirable in certain situations where the operator may want to align the C-arm by hand, the manual adjustment method can be difficult and time-consuming, especially if the person performing the medical procedure must also manipulate the C-arm. Additionally, this method of adjusting the position of the C-arm may lead to imprecise positioning by the operator or any other number of problems caused by human error.
Some conventional C-arm imaging machines have a drive train that is connected to the C-arm such that an operator can use the drive train to mechanically drive the C-arm to orbitally rotate about the carrier. The operator can thus control the movement of the C-arm by operating a joystick that is electrically connected to the drive train. However, often the C-arm imaging machines that incorporate such drive trains cannot be adjusted such that the C-arm is manually manipulated. Therefore, the C-arms may not be used in emergency situations where the drive train fails or there is no power. Additionally, conventional C-arms with drive trains are large fixed-room devices that cannot be moved out of a room for use. Additionally, the drive train is in a fixed position proximate the C-arm such that it cannot be moved with the C-arm and thus may take up space and get in  the way of operation of the C-arm. Additionally, there are other conventional C-arms that are mobile and incorporate a drive train, but these C-arms do not use a belt to drive the C-arm.
Therefore, a need exists for a mobile C-arm that may be manipulated either mechanically by a drive train or manually by an operator and that may be switched back and forth between such manipulation methods as necessary.